Analog signals are often stored in permanent form on magnetic tapes or disks which require the use of relatively cumbersome mechanical drive systems and which have, in many cases, relatively limited bandwidth capabilities. In systems which are intended to store analog signals by utilizing solid state techniques, the analog input signals are normally first converted to digital signals through the use of appropriate analog-to-digital converters, the signals in digital form being thereupon stored in binary solid state memories. In reading out such signals, the binary digital signals are appropriately read by utilizing digital techniques and the binary data is then converted to an analog signal through the use of suitable digital-to-analog conversion techniques. Such a procedure is also relatively cumbersome and in some cases, may be prohibitively expensive unless the process is limited to relatively low frequency input and output signals.
It is desirable to devise a system which will be essentially completely solid state in nature and will be capable of storing analog signals without the need to convert such signals to binary digital form. Such a system would be less cumbersome than the analog signal storage techniques discussed above, since it is capable of being fabricated in a much more compact form and, if made in sufficient quantities, is likely to be less expensive than presently used analog signal storage systems. Such a device should have a substantial commercial market, particularly if it were capable of storing either moderate bandwidth base-band signals or relatively wide-band RF signals.
In many applications it is desired that the analog signals be suitably processed, such as by obtaining a correlation thereof against a known reference signal or by performing Fourier transforms, and the like. An essential difficulty which is often encountered when implementing the desired signal processing function is that the time scale over which the data collection takes place does not match the time scale over which signal processing can be conveniently implemented in analog devices. Accordingly, such systems often must resort to digital techniques in order to achieve the storage function.
The development of a wide-band solid state analog storage system, however, would overcome the need for digital storage by providing a simple compact device for storing a collection of analog data so that it can be so processed. Such a memory would find a wide range of applications in many electronics, radar and communication systems, for example.